Comprehensive Guide to Sports Betting Terms and Definitions

A

• Accountant: Slang for a bookmaker or bookie.

• Ace: A trusted, reliable person (often someone you are comfortable betting through or taking info from).

• Action: The total amount of money wagered on a game or event, or the money one person has on the outcome of an event. See also: Handle.

• Action Reverse: A type of bet that combines two "if" bets. Both "if" bets must win for the action reverse to be successful.

• AFC: The American Football Conference, one of the NFL’s two conferences.

• Agent: A middleman who connects bettors to a sportsbook, often for credit play and a commission.

• Ahead: Net positive overall, meaning your wins exceed your losses.

• Ajax: UK slang referring to a betting tax.

• Alternative Line: Any spread or total that differs from the main line on a game, usually offered at adjusted odds so you can buy or sell points relative to the standard number.

• American Line: A hockey spread expressed in goals (a goals handicap) rather than a moneyline.

• American Odds: The +120/−150 format used by U.S. sportsbooks. They convert easily to implied probability for EV calculations.

• Angle: A strategy that tries to exploit rules, loopholes, or situations for an advantage.

• Arbitrage: Simultaneously betting on all possible outcomes of a game or event to guarantee a profit regardless of the result.

• Assumed Distribution (normal/empirical): A statistical shape used to translate a fair line in points into a win probability (e.g., assume margins are roughly normal, or use an empirical historical distribution).

B

• Back: To bet on an outcome to happen, typically used in exchange betting.

• Backer: A person who places bets on an outcome to happen, typically used in exchange betting.

• Backtest: A historical simulation to see how a strategy or model would have performed. It’s step one before risking real money.

• Bad Beat: A loss that is perceived as particularly unfair or unlucky due to unusual circumstances.

• Bank: The party “holding the risk” in a game, or simply another term for bankroll depending on context.

• Banker: A bet considered to have a high probability of winning, often used in parlay bets.

• Bankroll: The amount of money a bettor has set aside for betting purposes.

• Basic Strategy: A mathematically optimized decision framework for a casino game (most commonly blackjack).

• Bayes’ Theorem: A rule for updating a probability by combining your prior belief with how likely the new evidence is under that belief.

• Beard: A person who places bets on behalf of someone else to conceal the identity of the true bettor.

• Beef: A dispute between a bettor and a bookmaker (payout, grading, limits, etc.).

• Bet: The amount you risk on a wager (stake).

• Bet Spread: Your max bet size divided by your min bet size (a quick way to describe aggressiveness/variance in staking).

• Betting Exchange: A platform where bettors can bet against each other, with the exchange usually taking a commission on winning bets.

• Betting Limit: The minimum and or maximum stake a book will accept on a bet or market.

• Bettor: A person who places bets on sporting events or other outcomes.

• Blow Back: Giving back profits after being up, typically through bad bets or poor discipline.

• Book: Another term for a bookmaker or sportsbook.

• Bookie: Informal term for a bookmaker.

• Bookmaker: An individual or organization that accepts and pays off bets on sporting events. See also: Sportsbook.

• Bottle: UK slang for 2 to 1 odds.

• BR: Shorthand for bankroll.

• Break-Even Point: The point where total profits equal total losses over a sample.

• Breakeven Percentage: The win rate you must achieve on bets at a given set of odds to avoid losing money long-term. It’s calculated by dividing the risk by the total potential return (risk + reward).

• Buck: Slang for $100 (context matters; some people also use it loosely for $1).

• Buy: Buying points, adjusting a spread or total in your favor in exchange for worse odds.

• Buy Points: Paying extra to adjust the point spread or total in your favor.

• Buy Price: In spread or index betting, the higher of the two quotes (buy versus sell) used to price positions.

C

• Calibration: How well predicted probabilities match actual frequencies. For line models, you can judge calibration via performance vs. market closes derived from your fair lines.

• Canadian: A multi bet structure with 5 selections that creates 26 bets total (also called a Super Yankee).

• Canadian Line: A hockey line expressed as a moneyline (as opposed to a goals handicap).

• Card: A list of betting opportunities provided by a sportsbook for a particular day or event.

• Carpet: UK slang for 3 to 1 odds.

• Cash Out: A feature offered by some sportsbooks that allows bettors to settle their bet early for a reduced payout before the event concludes.

• Chalk: A significantly favored side in a game.

• Chalk-Eater/Chalk-Player: Someone who mostly bets favorites.

• Chartwriter: A tracker or analyst who records detailed performance notes, especially in racing.

• Circled Game: A game with reduced limits or special restrictions due to uncertainty (injuries, weather, lineup info).

• Closing Line: The final betting odds offered by bookmakers just before an event begins.

• Closing Line Value (CLV): The difference between the final betting line and the line at which a bettor placed their wager.

• Clone Joint: A sportsbook that copies other books’ lines instead of originating its own numbers.

• Consensus Line: A method for estimating the "fair" market line created by aggregating odds from multiple sharp sportsbooks, used as a baseline to remove bias from any single book’s number.

• Continuous (distribution): A probability model where outcomes can take any value within a range (not just whole numbers). Useful for modeling things like scoring margins treated as real-valued points; probabilities come from areas under a curve, not single points.

• Correlation: A measure (between -1 and 1) of how two variables move together. Positive correlation means they increase together; negative means one goes up while the other goes down.

• Correlated Parlay: A parlay bet where the outcome of one selection affects the outcome of another.

• Cover: When a team or selection beats the point spread.

• Credit Player: A bettor allowed to wager on credit up to a limit, settling later (often via an agent).

D

• Data Science: The practice of turning raw data into insights using math, statistics, programming, and domain knowledge. In sports betting, it means using data to understand odds, predict outcomes, and find edges.

• Dead Heat: When two or more selections finish a race or event in a tie, resulting in reduced payouts.

• Decimal Odds: Betting odds expressed as a decimal, commonly used in Europe and Australia.

• Degen: Slang term for a reckless or compulsive gambler.

• De-vig Conversion: The math used to remove the bookmaker’s vig from odds or lines, producing “fair” (no-vig) probabilities for apples-to-apples comparison.

• Derivative (Bet): A wager whose price is based on, or derived from, the main betting line for a game. Examples include first-quarter spreads, team totals, or alternate lines.

• Dime: A $1,000 bet.

• Dime Bet: A $1,000 wager (distinct from “a dime” as the amount itself).

• Dime Line: A 10 cent moneyline hold structure (smaller gap between favorite and dog prices).

• Discrete (distribution): A probability model where outcomes occur in separate, countable values (e.g., exact points scored or number of touchdowns). Probabilities are assigned to specific values rather than ranges.

• Dog: Short for "underdog," referring to the side expected to lose.

• Dollar: A $100 bet.

• Double Action: An if bet style setting where outcomes can be win, push, or cancel depending on the rules used.

• Double Result: A type of bet where the bettor predicts both the halftime result and the full-time result of a game or event.

• Doubleheader: Two games played by the same teams on the same day (most commonly baseball).

• Due For: The belief a team is “overdue” for a win or loss because of past results (a gambler’s fallacy).

E

• Earn: A bookmaker’s practical hold percentage, winnings divided by total handle.

• East Coast Line: A hockey pricing format that splits the goal handicap (for example 1 and 1.5) instead of using a single alt spread plus juice.

• Edge: A perceived advantage or insight that gives a bettor an increased chance of winning.

• Edge Case: A rare or extreme scenario at the boundary of normal conditions that can break assumptions, reveal bugs in models, or create unusual betting opportunities.

• Empirical (distribution): A probability distribution built directly from observed historical outcomes rather than a theoretical formula (like normal). It preserves real-world skew, fat tails, and quirks—useful for converting fair lines into probabilities that match actual game behavior.

• Even Money: A bet with odds of 1:1, +100, or 2.00 where the potential winnings equal the amount wagered. Also written as EV.

• Exotic Wager: Any bet other than a straight bet or parlay, often involving multiple variables or outcomes.

• Expected to Win Rate: An estimated long-run profit rate or ROI expectation for a bettor or model.

• Expected Value (EV): The long-term average profit or loss you can expect on a bet, calculated by multiplying each possible outcome by its probability and summing the results.

• Exposure: How much a book or bettor stands to lose from current positions.

• Extension: A book’s theoretical risk or liability on an event (similar to exposure, often used at the book level).

F

• Fair Line: The line your model says is correct. You compare this to the posted line to find edge.

• Favorite: The side expected to win.

• Features (inputs): The variables you feed a model (e.g., pregame spread, halftime margin). Good features are relevant, consistent, and available at bet time.

• Fifty Cents: Slang for a $50 wager.

• Final Four: The final four teams in the NCAA men’s basketball tournament.

• Firing: Betting large amounts aggressively.

• Fixed: An illegally predetermined outcome (match fixing).

• Fixed Odds: Betting odds that are agreed upon at the time the bet is placed and do not change.

• Flat Joint: A dishonest gambling operation or “rigged” game.

• Flea: Derogatory slang for a bettor who wagers tiny amounts and demands perks or special treatment.

• Foots: Slang for soccer.

• Form: A paper based view of expected performance, especially in racing.

• Fractional Odds: Betting odds expressed as a fraction.

• First-Half Points (FH): Total points scored in the first half.

• Front Money: A deposit posted to establish credit betting privileges.

• Future: A bet on a multi-stage event like an election, MVP award, or a tennis tournament.

G

• Gambler's Fallacy: The mistaken belief that previous outcomes affect future outcomes in games of chance.

• Get Down: Place a bet, typically meaning you successfully got your stake accepted.

• G-Note: Slang for $1,000.

• Going Down: Losing (either a bet or a run of bets).

• Grand: Slang for $1,000.

• Grand Salami: A hockey market betting the total goals across all games on a slate.

• Gross Win: Winnings before deductions like rebates, expenses, fees, or commissions.

H

• Half-Time Bet: A bet graded on first half performance (or a halftime result market, depending on the sport).

• Halftime Margin (HM): The score difference at halftime (home minus away).

• Handle: The total amount of money wagered by bettors on a particular event or over a specific period. See also: Action.

• Handicapping: Analyzing and predicting the outcome of sporting events, often involving factors such as injuries, weather conditions, and team statistics.

• Hedge: Placing bets on the opposite side of an initial wager to reduce potential losses and/or guarantee a profit.

• High Roller: A bettor who wagers large stakes.

• Holding Your Own: Roughly breaking even over a period.

• Home Field Advantage: The edge attributed to playing at home (crowd, travel, familiarity, officiating patterns).

• Home Run Hitter: A bettor who swings for big scores with high risk bets.

• Home Team: The team listed as home, typically shown second on many boards.

• Homoscedasticity: An Ordinary Least Squares assumption that prediction errors have similar variance across the range of predictions. Violations can distort inference and confidence.

• Hook: Half a point added to point spreads to prevent ties, often written as ".5" (e.g., 3.5 points).

• Hooked: Losing by the hook, meaning by half a point.

• Hoops: Slang for basketball.

• Hot: On a winning streak.

• Hot Game: A game attracting heavy sharp action or unusually concentrated action.

• Hot Tip: Early or insider info not fully in the market yet.

I

• IBF: International Boxing Federation.

• Implied Probability: The probability embedded in odds after conversion (e.g., from American odds). It lets you compare market prices to your model’s probabilities.

• In-Play Betting: Another term for live betting, where wagers are placed during the course of a game or event.

• Interaction Term: A feature created by multiplying two inputs (e.g., S0 × HM) to capture “it depends” effects.

• ​Interference: Illegal contact or obstruction that impacts play (often used in racing and some sports rules contexts).

J

• Juice: Another term for vigorish, representing the bookmaker's theoretical commission on a bet.

K

• Kelly (Kelly Criterion/fraction): A bet-sizing formula based on your edge and odds. Many bettors use a fraction of Kelly to control volatility.

• Kick It: Increase the size of a bet.

L

• Lay Bet: Betting on an outcome not to happen, acting as the bookmaker.

• Lay the Odds: Risk more than you can win (typical of betting a favorite price).

• Lay the Points: Bet a favorite giving points on the spread.

• Lay the Price: Bet a favorite on the moneyline.

• Layoff: Placing bets with other bookmakers to balance the risk of large wagers.

• Leak: A habit pattern that slowly drains winnings (tilt, chasing, bad sizing, bad markets).

• Leakage (Data Leakage): When future or out-of-sample information accidentally enters training or evaluation. It makes models look unrealistically good.

• Limit: The maximum amount a sportsbook will accept on a single bet.

• Line: The posted spread, total, or price for a market.

• Line Movement: Changes in the odds or point spread offered by bookmakers due to betting activity.

• Linemaker: The person or group that originates opening lines.

• Line Shopping: Comparing multiple sportsbooks to grab the best available price. Small improvements compound into real edge.

• Listed Pitcher (LP): A baseball rule where the bet is valid only if specified starting pitchers start (otherwise void or regraded per house rules).

• Liquidity: The amount of money and betting volume available in a market. Higher liquidity means you can place larger bets with less impact on the line and tighter, more efficient prices.

• Live Betting: Placing bets on a game or event while it is in progress. See also: In-play betting.

• Live One: A soft bettor, easy target, typically undisciplined or unskilled.

• Lock: A bet that is considered to be guaranteed to win, often used informally to describe a highly confident wager.

• Long Odds: Prices implying a low probability, meaning high payout if it hits.

• Long Shot: A bet with very low odds of winning, often associated with high potential payouts.

M

• MAE (Mean Absolute Error): The average absolute prediction error in points. Lower MAE means your fair-line predictions hug reality more closely.

  • How to calculate MAE:

    • For each game, find the miss: miss_i = |actual_i − predicted_i|

    • Add up all the misses

    • Divide by how many games you have

• Make-up figure: The re-deposit requirement you must meet before being eligible for certain bonuses again.

• March Madness: NCAA men’s basketball tournament nickname.

• Market Efficiency: A measure of how accurately betting odds reflect the true probabilities of outcomes. In an efficient market, lines adjust quickly to new information and leave little room for profitable bets. In less efficient markets, odds may be slow, mispriced, or exploitable.

• Martingale: A flawed betting strategy where the bettor doubles their stake after each loss, aiming to recoup previous losses with a single win.

• Middle: A betting strategy where a bettor places wagers on both sides of a game or event, hoping the final margin falls within a specific range to win both bets.

• Middler: Someone who frequently tries to middle games.

• MLB: Major League Baseball.

• Model: A mathematical or statistical framework used to estimate the probability of sports outcomes and identify value bets.

• Moneyline: A bet on which team will win a game outright, regardless of the point spread.

• Multicollinearity: When features are highly correlated, making regression coefficients unstable or “jumpy.” Regularization or pruning helps.

N

• NBA: National Basketball Association.

• NCAA: National Collegiate Athletic Association.

• NFC: National Football Conference (NFL).

• NFL: National Football League.

• NHL: National Hockey League.

• Nickel: A $500 bet.

• Newspaper Line: A non-official line published in papers, often stale or inaccurate.

• NIT: National Invitation Tournament (college basketball).

• Neutral Site: Venue where neither team has home advantage.

• Noise: Random or irrelevant information that looks useful but doesn’t actually predict outcomes.

• No-Vig (Fair) Odds/Probability: Odds or probabilities after removing the sportsbook’s vig. Use these to compare your model to the market without the house margin.

• Novelty Bet: A bet placed on non-sporting events or outcomes, such as political elections or entertainment awards.

O

• Odds: The probability of a particular outcome occurring, typically represented in American, decimal, or fractional format.

• Odds On Favorite: A favorite priced at better than even money (payout smaller than stake in many formats).

• Oddsmaker: The person or group that sets and moves lines (often used interchangeably with linemaker).

• Odds Screen: A live board of prices across multiple sportsbooks used for line shopping and tracking market movement.

• Off Lines: When one book’s line materially differs from the broader market.

• Official Line: The book’s actual line used to grade bets (not necessarily the “Vegas” number).

• Offshore Sportsbook: A sports betting site or establishment located outside the jurisdiction of the United States.

• Off the Board: An event temporarily unavailable for betting at a sportsbook, typically due to uncertainty or significant variables impacting the outcome.

• OLS (Ordinary Least Squares): The standard way to fit linear regression by minimizing the sum of squared errors. It’s fast, transparent, and a strong baseline.

• Opening Line: The initial point spread or odds set by bookmakers for an event.

• Out: A bookmaker or book.

• Outlaw Line: An early “test” line shown to select bettors before the full public opening.

• Out-of-Sample (OOS): Data the model hasn’t seen during training. True performance should be judged on OOS results.

• Outright Bet: A wager placed on the winner of an entire tournament or competition, rather than individual matches or games.

• Overtime: Extra play after regulation to determine a winner (or to complete scoring, depending on sport rules).

• Over/Under: A bet on whether the total score of a game will be over or under a specified number.

P

• Pace Proxies (drives/plays): Simple stats that hint at tempo. Faster pace tends to mean more possessions and scoring chances.

• Parimutuel Betting: A system of betting where all bets of a particular type are placed together in a pool, with the winnings divided among the winning bets after deductions.

• Parlay: A single bet that links together two or more individual bets for a higher payout.

• Past Performance: Historical performance record used to evaluate future prospects (especially racing).

• Payout: The amount returned on a winning wager (may include stake depending on context). Comparing payout to stake helps compute EV and bankroll impact.

• Penny Line: A moneyline that can move in 1 cent increments (tiny ticks), common in some markets.

• PGA: Professional Golfers’ Association.

• Pick: A selection made by a bettor for a particular game or event.

• Pick'em: A game or bet where neither side is favored, typically with a point spread of zero. Often written as “pk”.

• Plus Money: Another term for positive odds, indicating the potential profit is greater than the amount wagered.

• Point Spread: A margin of points set by bookmakers to even the odds between two teams.

• Post Up (Player): A bettor who deposits funds and wagers from that balance.

• Posterior: The updated probability after incorporating new evidence using Bayes’ Theorem.

• Pregame Market: Lines posted before a game starts (spread, total, moneyline). They’re typically the most efficient and hardest to beat.

• Press: Increase bet size, often after winning or when trying to push an edge.

• Pressing: Letting winnings ride or continually increasing stakes.

• Price: The odds you must lay or will receive on a bet.

• Prior: Your initial probability estimate before considering new evidence (often from base rates, models, or no-vig market odds).

• Probability: A number from 0 to 1 representing likelihood; in betting it is the backbone of implied probability and EV.

• Prop Bet (Proposition Bet): A wager on specific outcomes or events within a game or event that are not directly related to the final score.

• Puck: The hockey disc, and slang for hockey as a sport in some contexts.

• Punter: A bettor, particularly in the UK and Australia.

• Punter: UK and AUS term for a bettor.

• Push: When the result of a bet falls exactly on the point spread or total, resulting in a tie or refund.

• Push Rate: The percentage of bets that land exactly on the posted line, resulting in a “push” (no win, no loss, stake returned). Tracking push rate matters because it affects the true value of spreads and totals.

• Python: A popular programming language known for being beginner-friendly and powerful. Widely used in betting, modeling, and AI because of its math and data libraries.

Q

• Quant: Short for “quantitative analyst.” Someone who uses math, statistics, and data models to make decisions. In betting, a quant builds models to price games and spot edges rather than relying on intuition.

R

• R: A programming language built for statistics and data visualization. It’s especially strong in running models, exploring data, and creating graphs.

• Rain Out: Event canceled due to weather.

• Regression: A statistical method used to estimate the relationship between one outcome and one or more predictors.

• Regularization (Ridge/Lasso): Penalties added during training to prevent overfitting and stabilize coefficients. Helpful when features are correlated or models are noisy.

• Residuals: The differences between what your model predicted and what actually happened. Analyzing residuals helps check how well your model works.

• Return: The total amount of money a bettor receives if their bet is successful, including the original stake and any winnings.

• RMSE (Root Mean Squared Error): The square-root of average squared error; it penalizes large misses more than MAE.

  • Calculating RMSE:

    • For each game, compute the miss: miss_i = actual_i − predicted_i

    • Square each miss: miss_i^2

    • Average the squared misses

    • Take the square root

• Rollover: The number of times a bettor must wager their deposit or bonus funds before being able to withdraw winnings.

• Round Robin: A type of bet that combines multiple parlays on a group of selections, resulting in a series of smaller bets.

• Run Line: A type of point spread bet used in baseball, where the favored team must win by a certain number of runs or the underdog must lose by fewer runs than the spread.

• Rundown: A readout of current lines and prices offered by a sportsbook.

• Running Bad: On a losing streak (often with an implied “unlucky” tone).

• Running Good: On a winning streak.

• R-Squared (R²): A number between 0 and 1 that shows how much of the variation in the outcome your model explains. Higher values mean your predictors fit the data better.

• Ryder Cup: A major international golf competition between teams representing Europe and the USA.

S

• Scalper: A bettor who tries to lock in small profit from price differences between books, typically with rapid, tight execution.

• Score: Win a large amount, often from a big bet or a longshot.

• Scout: Someone who gathers info and reports it to handicappers or betting groups.

• Scratch: Withdraw or cancel, or in racing a participant is removed from the event.

• Second-Half (2H) Line: A live line posted at halftime that prices only quarters 3 and 4.

• Second-Half Bet: A bet graded only on the second half of play.

• Shading: When a sportsbook deliberately moves a line or price slightly away from its true number (often toward popular sides or overs) to account for public bias and increase its expected profit.

• Sharp: A professional or knowledgeable bettor who consistently makes well-informed wagers. See also: Wise Guy.

• Short Odds: Heavy favorite pricing with small payout.

• Shortstop: Slang for someone who bets small.

• Side: A team or outcome you bet on (as opposed to the total), sometimes also used to describe spread bets specifically.

• Sides: The two opposing teams or the two sides of a market.

• Signal: The useful information that truly explains or predicts outcomes. In betting, signal might come from reliable stats, market movement, or proven models.

• Single Action: An if bet rule where only wins advance, with pushes canceling per house rules.

• SlipSync (bet logging): A tool to automatically record bets from screenshots into your tracker. Reduces manual errors and speeds up analysis.

• Smart Money: Action believed to come from skilled bettors.

• Soft Line: A stale or mispriced line that has not caught up to true market value.

• Splash Around: Bet loosely, undisciplined, or outside your normal criteria.

• Sport Player: A casual bettor who mostly bets for fun and occasionally fires when they feel strongly.

• Sportsbook: A facility, website, or establishment that accepts bets on sporting events. See also: Bookmaker.

• Spread Limit: A bet sizing structure where allowed bet amounts must fall within a defined range each round (more common in poker contexts).

• Square: An inexperienced or casual bettor who typically bets for entertainment rather than profit.

• Stake: The amount of money wagered on a single bet. See also: Wager.

• Stale: Describes a line or price that hasn’t updated to reflect new information or market movement, often creating a temporary value opportunity for bettors.

• Stanley Cup: NHL championship trophy.

• Steam: Rapid and significant line movement across multiple sportsbooks, usually due to heavy betting activity by sharps.

• Steaming: Betting recklessly or playing wildly, often while emotional or tilted.

• Stress Test (segmenting): Evaluating how your model or strategy performs in difficult slices (e.g., big halftime leads, extreme totals). Shows whether your edge holds across states.

• Straight Bet: A single bet placed on a single outcome, also known as a "straight wager" or "single bet."

• Stuck: Down money overall, feeling buried.

• Sucker: A soft bettor with poor skill or discipline.

• Sucker Bet: A wager priced in a way that heavily favors the book (structurally negative EV).

• Sudden Death: Overtime where the first score ends the game.

• Super Bowl: NFL championship game.

• Syndicate: A group of bettors who pool money, resources, and expertise to wager collectively, often with advanced models or specialized roles.

• Synthetic Line: The effective “fair” price you get by combining the best sides of related markets or different sportsbooks to create a near-zero-hold synthetic market.

• System: A formula based betting approach, often marketed as “automatic,” sometimes legitimate, often not.

T

• Take a Price: Bet an underdog on the moneyline.

• Take the Odds: Risk less to win more, typically taking plus money.

• Take the Points: Bet the underdog plus points on the spread.

• Teaser: A type of bet that allows the bettor to adjust the point spread or total in their favor for reduced odds.

• Ten-Cent Line: Moneyline structure where the favorite and dog prices differ by about $0.10 in implied vig terms.

• Thirty-Cent Line: Wider moneyline structure with larger built-in hold than a 10 cent line.

• Tie: A draw, neither side wins.

• Tipster: Someone who provides betting tips or predictions, often for a fee or tips in exchange.

• Toss Up: A near pick’em matchup, no clear favorite.

• Totals: Over under markets based on combined scoring (or other aggregated stats).

• Tout: Someone who sells or promotes their expertise in sports betting picks or predictions.

• Tout Service: A business that sells picks or betting opinions.

• Triple Sharp: Slang for an extremely strong sharp bettor.

• Twenty Cent Line: Moneyline structure with medium hold between 10 cent and 30 cent styles.

• Tweener: A sportsbook that posts numbers between other books instead of leading.

U

• Underdog: The side priced as less likely to win, usually offering plus money or receiving points.

• Underlay: A bad price where the odds are worse than fair value (the opposite of a value overlay).

• Unit: A standardized measurement used by bettors to quantify the size of their wagers relative to their bankroll.

V

• Value: A bet that is deemed to have favorable odds compared to the perceived probability of the outcome occurring.

• Variance: A measure of how spread out results are from the average. Higher variance means swingier results; lower variance means outcomes cluster near expectations.

• Version Log (model log): A simple record of model changes and results. It prevents you from losing track of what worked and why.

• Vigorish (Vig): The theoretical commission that a bookmaker charges for accepting a bet.

• VIP: A high value bettor who receives special treatment (limits, promos, comps).

• Visitor: The away team.

• Void: A bet canceled with stake returned, effectively no action.

W

• Wager: The amount of money placed on a bet.

• Walk-Forward Testing: Training on past seasons and testing on the next season in order. This prevents “peeking” at the future and gives a truer read on performance.

• WBA: World Boxing Association.

• WBC: World Boxing Council.

• Wise Guy: Another term for a sharp or professional bettor. See also: Sharp.

• WNBA: Women’s National Basketball Association.

• Wong Teaser: A specific type of NFL teaser that moves spreads through key numbers 3 and 7 (typically a 2-team, 6-point teaser), originally shown to be +EV at older pricing like -110. See also: Teaser

• ​World Series: MLB championship series.